BOSTON (Reuters) - A protein found naturally in the body could bring scientists a step closer to developing a natural and effective diet pill, a new British study said on Wednesday.
Volunteers injected with the protein PYY two hours before mealtime consumed 30 percent fewer calories when they sat down to eat, without experiencing any difference in the taste of the food or other apparent side effects.
Injections of PYY two hours before mealtime cut the appetite of fat and skinny people, and did so without affecting the taste of the food or causing other apparent side effects.
"PYY appears to be a major factor limiting appetite after meals," researchers from Hammersmith Hospital in London said in Thursday's New England Journal of Medicine (news - web sites), where their study was published.
But it could be a while before the latest PYY research benefits consumers who are overweight -- like the 59 million obese people in the United States alone.
Long-term tests have not been done, and the protein, also known as peptide YY3-36, cannot be taken in pill form because it is quickly broken down by the stomach.
Scientists would have to develop a more resilient form or discover a chemical that mimics PYY, which is released by the cells lining the intestine, travels through the blood and fools the brain into thinking that the body has been fed.
PYY is one of more than two dozen hormones known to regulate appetite and energy. Among those are ghrelin, which is released by the stomach and upper intestine and causes feelings of hunger.
Researchers had hoped that leptin, a hormone found in body fat, would help with weight loss after tests showed it helped limit hunger. But experiments showed that obese people have a resistance to leptin.
The New England Journal study, led by Rachel Batterham, found that PYY did not have the same limitation.
Two hours after PYY was given intravenously, the 12 obese patients ate 30 percent fewer calories from an all-you-could-eat buffet than they did after a salt water injection. Twelve lean volunteers ate 31 percent fewer calories.
The effect persisted for at least another 10 hours, and even after 24 hours, people in the obese group had eaten 17 percent fewer calories.
"We found that obese subjects were not resistant to the anorectic effects of PYY," the researchers concluded.
They also found that PYY levels were naturally low in obese volunteers, which may be a reason why they were overweight.
In a commentary in the Journal, Judith Korner and Rudolph Leibel of Columbia University in New York said any one substance was unlikely to be a "magic bullet" for weight loss because hunger is so complex.
They said a successful drug would probably target "the interlocking, redundant systems that drive food intake and act to resist the loss of body fat."
The PYY used in the study was supplied by Bachem AG of Switzerland.